Conventionally, with fuel cell systems, there are systems which circulate hydrogen gas as the fuel gas, and as the impurities within the fuel gas increase, execute exhausting of a portion of the exhaust gas to outside the circulation system, a so-called “purge operation.” Then, for example, with the technology of Patent Document 1, when it is determined that a purge operation has been executed, after the point in time when the exhaust and drainage valve is open (on), spraying of hydrogen gas to the fuel cell from the injector is stopped, and the hydrogen pump is stopped so circulation of hydrogen gas from the circulation flow path to the hydrogen supply flow path is stopped. Meanwhile, when it is determined that a purge operation has not been operated, the normal control of the injector continues. Specifically, the injector's gas spray time and gas spray timing are controlled, regulating the flow volume and pressure of the hydrogen gas supplied to the fuel cell.